A mathematical framework for evaluation of column shape profiles for an advanced gas-cooled reactor core model subject to seismic excitation

• Published in: Nuclear engineering and design Vol. 391; p. 111735
• Main Authors: White, R.E., Gokce, T., Oddbjornsson, O., Bourne, K., Crewe, A.J., Dihoru, L., Horseman, T., Dietz, M., Kloukinas, P., Taylor, C.A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2022; Elsevier BV
• Subjects: Advanced gas cooled reactor; Bricks; Channels; Column shape displacement; Control rods; Correlation coefficients; Displacement; Displacement analysis; Earthquake loads; Earthquakes; Fuels; Gas cooled reactors; Mathematical analysis; Mechanics (physics); Motion capture; Neutrons; Nuclear fuels; Nuclear power plants; Nuclear safety; Power plants; Reactor cores; Reactors; Seismic activity; Seismic response; Seismic testing; Shutdowns; Stacked column; Statistical analysis; Vision systems; Column shape displacement; Seismic testing; Stacked column; Advanced gas cooled reactor; Displacement analysis
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2022.111735

•An experimental Nuclear Advanced Gas-cooled Reactor core-like structure model is studied under seismic loading.•Global dynamic behaviour of stacked brick columns are studied using direct measurements of brick interface displacements.•A mathematical framework is proposed to indirectly evaluate column shape profiles of instrumented stacked brick columns.•Column shape profile algorithm is validated against a separate displacement tracking system demonstrating good performance.•The instrumented columns exhibit significantly larger seismic responses in the presence of large numbers of cracked bricks. The safe shutdown of Advanced Gas-cooled Reactor (AGR) nuclear power stations in response to a seismic event is vital to their safety case. The tubular graphite bricks used to moderate the neutrons within an AGR core are arranged in columns whose bores provide channels for either fuel or control rods. Earthquake-induced distortion of the channels could impede the insertion of the control rods and compromise the safe shut-down, maintenance and servicing of the reactor. This paper presents a mathematical framework, utilising Euler mechanics, to evaluate the column shape displacement profiles of fuel and control rod channels within a state-of-the-art quarter-sized physical model of an AGR core when subjected to seismic loading. The data obtained from sensors installed within the model bricks, and configured to monitor interface displacements, are used to infer the global behaviour of a multi-stacked brick column subject to seismic excitation. Directly measured displacements of the top of the brick columns, obtained using a motion capture vision system, are compared with the displacements calculated using the framework presented, verifying the validity of the procedure. Statistical analysis is employed to quantify and characterise the performance of the Euler mechanics method. For multiple model build configurations, which represent different brick-cracking scenarios in an aged core, the Pearson correlation factor between the direct and indirect measurements is evaluated for the top of the column displacements giving an average value of 0.96 in the direction of the input motion. This shows that good agreement is achieved for the column shape displacement time-histories. The seismic responses are shown to be significantly larger in amplitude in the presence of large numbers of cracked bricks.